I think the design considerations for a good 4e module are different from those of a good 1e or 3.x module. Just converting the stats probably wouldn't cut it, in my opinion. And with an increasing number of modules being released for my preferred system (or one that is highly compatible in its stats and approach to the game), a 4e module with converted stats would be very low on my list of likely purchases.
From my experience I think you and everyone else who says it would translate badly between editions are wrong.
Why? I have used the 4E Punjar modules, all of the, converted to my C&C game.
I have also done the same with modules from every single edition of D&D, and they all "translate" just fine to C&C.
Plus you people need to remember, if your playing 4E your PC's and your game to game rules of movement, etc... are already taken care of by YOU, not the module.
Same deal if your playing 3E.
Same deal for any other RPG your running.
Plus I don't know about the rest of you, but the number of monsters and the amount of treasure given in a module has never been followed by me UNLESS I thought my group could handle the creatures as written and the treasure was to my liking to begin with.
Apparently a lot of you only run modules exactly as written and never change anything.
So if you think having 5 foot squares instead of 10 foot squares, or having too many monsters or too few, or the treasure isn't "just right", not having done perfectly right for you is a "game breaker" then I am rather disappointed, I have always had this image that RPGers were creative and thrived on adaptation and improvisation, apparently I have been wrong all this time.